1. Field of the Invention
The present invention relates to a device and a method for judging a wheel ground-contact state, and a vehicle motion control device.
2. Description of the Related Art
There is known a method of controlling a vehicle motion state in consideration of a ground contact state of wheel from the viewpoint of enhancing safety of a vehicle when the vehicle is turning. According to this control method, it is required to monitor the ground-contact state of the wheel, and thus the ground-contact state is estimated on the basis of a roll angle occurring in the vehicle or a roll angular velocity. This is because when rolling occurs in the vehicle, the wheels of the vehicle are inclined with respect to the ground surface, and thus the deterioration of the ground-contact state can be judged on the basis of the degree of the inclination concerned. When it is judged that the ground-contact state of the wheel is not good (or fine), the roll rigidity of the vehicle is increased to suppress the roll angle occurring in the vehicle, whereby the ground-contact state of the vehicle is getting better and thus the safety of the vehicle when the vehicle is turning can be enhanced. For example, JP-A-2001-050973 discloses a method of estimating the behavior of a vehicle by measuring a roll angle or roll angular velocity. Furthermore, JP-A-2002-012141 discloses a general method concerning roll control of a vehicle.
However, in the method of estimating the ground-contact state of the wheel on the basis of the roll state of the vehicle, the ground-contact state of the vehicle is indirectly estimated, and thus it is difficult to judge the ground-contact state of the wheels with high precision.